U.S. patent application number 14/781322 was filed with the patent office on 2016-04-14 for process for manufacturing lithium carboxymethyl cellulose.
This patent application is currently assigned to Dow Global Technologies LLC. The applicant listed for this patent is DOW GLOBAL TECHNOLOGIES LLC. Invention is credited to Roland Adden, Alexandra Hild, Hans-Juergen Juhl.
Application Number | 20160102153 14/781322 |
Document ID | / |
Family ID | 50983204 |
Filed Date | 2016-04-14 |
United States Patent
Application |
20160102153 |
Kind Code |
A1 |
Hild; Alexandra ; et
al. |
April 14, 2016 |
PROCESS FOR MANUFACTURING LITHIUM CARBOXYMETHYL CELLULOSE
Abstract
Prepare lithium carboxymethyl cellulose by treating sodium
carboxymethyl cellulose with a weak acid to form an acid from of
carboxymethyl cellulose and then treating the acid form of the
carboxymethyl cellulose with lithium chloride.
Inventors: |
Hild; Alexandra; (Soltau,
DE) ; Juhl; Hans-Juergen; (Bad Fallingbostel, DE)
; Adden; Roland; (Bomlitz, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DOW GLOBAL TECHNOLOGIES LLC |
Midland |
MI |
US |
|
|
Assignee: |
Dow Global Technologies LLC
Midland
MI
|
Family ID: |
50983204 |
Appl. No.: |
14/781322 |
Filed: |
May 28, 2014 |
PCT Filed: |
May 28, 2014 |
PCT NO: |
PCT/US2014/039640 |
371 Date: |
September 30, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61830659 |
Jun 4, 2013 |
|
|
|
Current U.S.
Class: |
536/98 |
Current CPC
Class: |
C08B 15/00 20130101;
C08B 11/12 20130101 |
International
Class: |
C08B 11/12 20060101
C08B011/12 |
Claims
1. A process comprising the following steps: (a) treating sodium
carboxymethyl cellulose with a weak acid to form an acid form of
carboxymethyl cellulose; and (b) treating the acid form of
carboxymethyl cellulose with lithium chloride to form lithium
carboxymethyl cellulose.
2. The process of claim 1, further characterized by the weak acid
being selected from a group consisting of acetic acid, formic acid,
hydrofluoric acid, nitrous acid, hydrocyanic acid and hydrogen
sulfate ion.
3. The process of claim 1, further characterized by the weak acid
being acetic acid.
4. The process of claim 1, further characterized by an absence of
strong acid during the forming of carboxymethyl cellulose in step
(a).
5. The process of claim 1, further characterized by the treatments
of step (a) and step (b) being done in an aqueous solution.
6. The process of claim 5, further characterized by the aqueous
solution comprising alcohol.
7. The process of claim 1, further characterized by the sodium
carboxymethyl cellulose having a degree of substitution in a range
of 0.4 to 2.0.
Description
BACKGROUND OF THE INVENTION
Field of the Invention
[0001] The present invention relates to a method for manufacturing
lithium carboxymethyl cellulose.
INTRODUCTION
[0002] Lithium carboxymethyl cellulose (Li-CMC) is a possible
binder material for use in lithium ion (Li-ion) batteries.
Traditional binder systems typically have used polyvinylidene
fluoride (PVDF) as a polymeric binder and N-methyl-2-pyrrolidone
(NMP) as a solvent for the binder. The fluorinated binder and
hazardous solvent prove challenging to safely handle and dispose.
Li-CMC is an alternative binder that can be delivered using an
aqueous solvent. As a result, use of a Li-CMC binder can reduce the
hazards associated with the binder system of Li-ion batteries and
disposal concerns associated with both the binder and the solvent.
However, manufacturing Li-CMC can be challenging.
[0003] Carboxymethyl cellulose (CMC) is commonly available as a
sodium salt (Na-CMC) due to specific manufacturing conditions that
include alkalization of cellulosic raw material with caustic soda
followed by etherification and neutralization. Therefore,
essentially all commercially available CMC is Na-CMC.
[0004] CN102206286A discloses a method for converting Na-CMC to
Li-CMC using hydrochloric acid. The reference discloses treating
Na-CMC with an aqueous hydrochloric acid solution and then treating
the resulting acid form of CMC (H-CMC) with an aqueous lithium
hydroxide solution to achieve Li-CMC. Unfortunately, treating
Na-CMC with hydrochloric acid (a strong acid) generally degrades
the CMC polymer and risks corrosion of processing equipment.
Additionally, the resulting Li-CMC requires a drying step that can
cause crosslinking by re-esterification of the carboxylate
groups.
[0005] Other methods for converting Na-CMC to Li-CMC include
treating with a concentrated aqueous lithium hydroxide solution
followed by etherification with chlorine acetic acid. (see, e.g.,
Machado, G. D. et al., Polimery, 48, 4 (2003) 273-279; and
Abuh-Lebdeh et al., Journal of Power Sources, 196 (2011)
2128-2134). However, lithium hydroxide has insufficient strength to
fully solubilize the cellulose chain for the subsequent
etherification step. It is also known to prepare Li-CMC using an
ion exchange column. (See, Abuh-Lebdeh et al, Journal of Power
Sources, 213 (2012) 249-254). However, an ion exchange column
process is a low volume process that can only produce small
quantities of Li-CMC.
[0006] There is a need for a less challenging method for
manufacturing Li-CMC that does not suffer from the handicaps of the
prior art.
BRIEF SUMMARY OF THE INVENTION
[0007] The present invention offers a method for manufacturing
Li-CMC that avoids the process challenges of the prior art. The
process of the present invention does not require use of strong
acid such as hydrochloric acid or the use of lithium hydroxide
solution followed by chlorine acetic acid or use of an ion exchange
column.
[0008] Surprisingly, the present invention is a result of
discovering that treating Na-CMC with a weak acid to form the CMC
acid followed by treating the CMC acid with lithium chloride
effectively produces Li-CMC in a safe, cost-effective manner
without the problems associated with the prior art.
[0009] In a first aspect, the present invention is a process
comprising the following steps: (a) treating sodium carboxymethyl
cellulose with a weak acid to form an acid form of carboxymethyl
cellulose; and (b) treating the acid form of carboxymethyl
cellulose with lithium chloride to form lithium carboxymethyl
cellulose
DETAILED DESCRIPTION OF THE INVENTION
[0010] "Multiple" means two or more. "And/or" means "and, or as an
alternative". All ranges include endpoints unless otherwise
indicated. All volume percents are determined at 23 degrees Celsius
(.degree. C.).
[0011] The process of the present invention requires treating
sodium carboxymethyl cellulose (Na-CMC) with a weak acid to form an
acid form of carboxymethyl cellulose (H-CMC). Weak acids are acids
that incompletely ionize when dissolved in water. Examples of weak
acids include acetic acid, formic acid, hydrofluoric acid,
hydrocyanic acid, nitrous acid and hydrogen sulfate ion. A
particularly desirable weak acid for use in this step for the
present invention is acetic acid. Weak acids are in contrast to
strong acids. Strong acids fully dissociate upon dissolving in
water. Examples of strong acids include hydrochloric acid, nitric
acid, sulfuric acid, hydrobromic acid, hydroiodic acid and
perchloric acid. Desirably, the process of the present invention is
free of strong acid during the formation of H-CMC. Preferably, the
entire process of the present invention is free of strong acid.
[0012] The Na-CMC desirably has a degree of substitution that is
0.4 or more, preferably 0.5 or more, still more preferably 0.6 or
more and at the same time desirably is 2.0 or less, preferably 1.6
or less, more preferably 1.3 or less. Having a degree of
substitution in this range ensures that it is water soluble.
[0013] Degree of substitution for Na-CMC refers to the average
number of hydroxyl (OH) groups in one anhydroglucose unit that have
been substituted with another group. Determine degree of
substitution according to ASTM D 1439-03 "Standard Test Methods for
Sodium Carboxymethylcellulose; Degree of etherification, Test
Method B: Nonaqueous Titration". In brief, the method involves
treating a solid sample of Na-CMC with glacial acetic acid at
boiling temperature to cause a release of acetate ion equivalent to
the sodium carboxymethyl groups. These acetate ions are titrated as
a strong base in anhydrous acetic acid using a perchloric acid
standard solution. Determine the titration end point
potentiometrically. Other alkaline salts of carboxylic acids (for
example, sodium glycolate and di-sodium diglycolate) behave
similarly and are co-titrated.
[0014] Generally, treatment of Na-CMC with a weak acid to form
H-CMC is done in an aqueous solution where Na-CMC and weak acid are
added to an aqueous solvent. For example, one method of treating
Na-CMC with a weak acid within the scope of the present invention
is by dispersing Na-CMC into a solvent to form an initial
dispersion and then adding weak acid to the initial dispersion. The
solvent comprises water and one or more than one organic co-solvent
that is miscible or soluble with water. Desirable co-solvents
include any one or combination of more than one of alcohols and
acetone. Suitable alcohols for use as co-solvents include one or
any combination of more than one selected from methanol, ethanol,
n-propanol and iso-propanol as well as butanol isomers. The aqueous
solvent consists of water and co-solvent. Co-solvent typically
accounts for 70 volume-percent (vol %) or more, preferably 80 vol %
or more and can be 90 vol % or more and at the same time typically
accounts for 95 wt % or less, and can be 90 wt % or less, 85 wt %
or less and even 80 wt % or less based on total solvent volume. At
the same time, water typically accounts for 5 wt % or more,
preferably 10 wt % or more and can be 15 wt % or more while at the
same time typically accounts for 30 vol % or less, preferably 20
vol % or less and can be 10 vol % or less based on total solvent
volume. Determine wt % of water and co-solvent relative to combined
weight of water and co-solvent.
[0015] The temperature of the conversion of Na-CMC to H-CMC is not
critical as long as it is below the boiling temperature of the
solvent at the pressure the conversion is conducted. Typically,
conduct the conversion reaction at a temperature of 10 degrees
Celsius (.degree. C.) or higher, preferably 15.degree. C. or
higher, still more preferably 20.degree. C. or higher, yet more
preferably 22.degree. C. or higher. The conversion reaction can be
run at temperatures of 25.degree. C. or higher, even 30.degree. C.
or higher and even 50.degree. C. or higher.
[0016] Desirably, continue to agitate the dispersion throughout the
reaction. It is also desirable to maintain the solids concentration
in the dispersion at 15 weight-percent (wt %) or less, preferably
10 wt % or less, still more preferably 8 wt % or less and at the
same time is it desirable to maintain the solids concentration in
the dispersion at one wt % or more, preferably 3 wt % or more,
still more preferably 5 wt % or more with wt % of solids based on
combined weight of solids and solvent. The total reaction time is
desirably at least five minutes, preferably 15 minutes or more,
more preferably 30 minutes or more, yet more preferably 45 minutes
or more and even more preferably 60 minutes or more. There is no
known technical upper limit on the reaction time, but practically
the reaction time is generally two hours or less.
[0017] Convert the H-CMC to lithium carboxymethyl cellulose
(Li-CMC) by treating the H-CMC with lithium chloride. Generally,
the H-CMC is isolated by filtration after completing the
acidification of Na-CMC and a solution of lithium chloride is added
to the isolated H-CMC. The solvent of the lithium chloride solution
is typically a solvent as described for the conversion of Na-CMC to
H-CMC. Desirably the aqueous component of the solvent is saturated
with lithium chloride to maximize the amount of lithium chloride in
the solution. The lithium chloride reacts with the H-CMC to form
Li-CMC. The conversion of H-CMC to Li-CMC is desirably conducted at
a temperature as described for the conversion of Na-CMC to
H-CMC.
[0018] The Li-CMC can be isolated by removing the solvent phase.
Preferably, the Li-CMC is washed with additional solvent to remove
impurities. The Li-CMC can be dried to remove residual solvent.
Drying can be done at an elevated temperature such as 50.degree. C.
or higher, 55.degree. C. or higher, even 60.degree. C. or higher.
Generally, dry at a temperature of 105.degree. C. or lower.
[0019] The process of the present invention provides a method for
converting Na-CMC to Li-CMC without requiring use of a strong acid
or the use of lithium hydroxide. In that regard, the process of the
present invention can be free of strong acid, lithium hydroxide or
both strong acid and lithium hydroxide. Moreover, the process of
the present invention offers a means for high volume production of
Li-CMC in contrast to small quantity production possible form
exchange column processes.
[0020] The following example illustrates an embodiment of the
present invention.
Example
[0021] Disperse 50 grams (g) of Na-CMC (degree of substitution in a
range of 0.6-2.0; for example, WALOCEL.TM. CRT 2000 PA, WALOCEL is
a trademark of The Dow Chemical Company into 700 g of a solvent
consisting of 50 volume percent (vol %) methanol, 50 vol %
iso-propanol and 20 vol % purified water at approximately
23.degree. C. Dropwise add 26.4 g glacial acetic acid to the
dispersion and stir for one hour at approximately 23.degree. C. to
form a dispersion of H-CMC. Isolate the H-CMC from the solvent by
filtration.
[0022] Form a solution of lithium chloride consisting of 50 vol %
methanol, 30 vol % iso-propanol and 20 vol % purified water
saturated with lithium chloride at a temperature of approximately
23.degree. C. Disperse the isolated H-CMC into 700 grams of the
lithium chloride solution. Stir the resulting dispersion for 15
minutes. Isolate solids from liquids by filtration. Again disperse
the isolated solid into a lithium chloride solution, mix for 15
minutes and isolate by filtration. Repeat three times and isolate
the product by filtration.
[0023] Wash the isolated product with 700 grams of a solvent (20
vol % water, 50 vol % methanol and 30 vol % isopropanol) and
isolate by filtration. Repeat three times and isolate the final
product by filtration. Dry the final product for 12 hours at
55.degree. C. The final Li-CMC is water soluble. 80 percent of the
carboxymethyl groups in the resulting Li-CMC have sodium ions
replaced with lithium, as determined by ion exchange chromatography
after acidic hydrolysis using 4 M HNO.sub.3. The procedure for the
ion exchange chromatography include adding 5 milliliters of HNO3 (4
moles per liter of deionized water) to 200 milligrams of Li-CMC in
a 20 milliliter pressure tight vial. Herein, deionized water
contains less than 0.01 milligrams per liter of sodium, potassium
and lithium ions. Seal the vial with a crimp cap comprising a
polytetrafluoroethylene coated septum. Heat the vial and its
contents to 100 C, mix thoroughly by shaking and heat another 10
minutes at 100.degree. C. Allow the vial and contents to cool to
approximately 23.degree. C. and transfer the vial contents to a 1
liter volumetric flask that is then filled with deionized water and
use this solution for ion exchange chromatography after filter
(syringe filter, 0.45 micrometer Nylon, FA. Nalgene, Art.-Nr.
196-2045). Conduct ion exchange chromatography according to the
procedure set forth in the Product Manual for IonPac.TM. CG 12A and
IonPac.TM. CS 12 A Columns by Thermo Scientific (IonPac is a
trademark of Dionex Corporation). Conduct ion exchange
chromatography with Suppressor technique and conductibility
detector DX120 with autosampler using data system Chromeleon 6.3,
precolumn (IonPac CB12A), separation column (IonPac CS12A),
self-regenerating suppressor for cationics CSRS300 and sample bin
for auto sampler (Polyvial 10 milliliters).
[0024] The WALOCEL CRT 2000 PA (238 grams per mole) has a 2%
aqueous solution viscosity of 2130 milliPascals*seconds and the
final Li-CMC (226 grams per mole) has a 2% aqueous solution
viscosity of 3700 milliPascals*seconds.
* * * * *